Air Force Space Surveillance System

There were three transmitter sites in the system:[3]

• 216.983 MHz at Lake Kickapoo, Texas (33°32′47″N 98°45′46″W) (Master transmitter)
• 216.97 MHz at Gila River, Arizona (33°06′32″N 112°01′45″W)
• 216.99 MHz at Jordan Lake, Alabama (32°39′33″N 86°15′52″W).

The master transmitter at Lake Kickapoo was said to be the most powerful continuous wave (CW) station in the world, at 768 kW radiated power on 216.97927 MHz.

When the system became operational in 1961, the original frequency was 108.50 MHz (just above the FM broadcast band). In 1965 the "Fence" system was modernized with the operating frequency doubled to 216.98 MHz (just above Channel 13 in the VHF TV broadcast band) to obtain higher resolution and to locate smaller objects. This frequency was used until the Fence was decommissioned in 2013. Fill-in transmitter sites at Gila River and Jordan Lake used offset frequencies listed above from the early 1990s to 2013 to help better detect which transmitter "illuminated" an object in space, as multiple transmitters could have illuminated the same object at the same time. Overhead imagery (see coordinates given above) of the Gila River and Jordan Lake sites shows the original design at the lower frequency.

There were six receiving stations:[3]

• San Diego, California (32°34′42″N 116°58′11″W)
• Elephant Butte, New Mexico (33°26′35″N 106°59′50″W)
• Red River, Arkansas (33°19′48″N 93°33′01″W)
• Silver Lake, Mississippi (33°08′42″N 91°01′16″W)
• Hawkinsville, Georgia (32°17′20″N 83°32′10″W)
• Tattnall, Georgia (32°02′35″N 81°55′21″W).

The following receiving stations were placed in cold storage in April 2013:

• Silver Lake, Mississippi (33°08′42″N 91°01′16″W)
• Tattnall, Georgia (32°02′35″N 81°55′21″W).

The receiving stations at Elephant Butte and Hawkinsville were considered to be "High Altitude" stations with longer and more complex antenna systems that are designed to see targets at higher altitudes than the other four receiving stations.

Author Curtis Peebles notes that the original "Space Fence" or Space Surveillance System began operations in 1959.[4] The system predated the formation of NORAD and was known as the U.S. Navy Space Surveillance System (or SPASUR or NAVSPASUR).[5] From 1960 until the early 1990s the system was used in conjunction with a network of Baker-Nunn cameras that could see "an object the size of a basketball at 25,000 miles."[4][6]

The system was formerly operated by the U.S. Navy for NORAD from 1961 until October 2004. Initially independent as NAVSPASUR, it was ran by Naval Space Command from 1993, and finally by Naval Network and Space Operations Command from 2002 until command was passed to the Air Force 20th Space Control Squadron on October 1, 2004.[1]

In 2009, the operations and maintenance contract for the day-to-day management and operation of the Fence was awarded to Five Rivers Services, LLC, based in Colorado Springs, Colorado. On September 30, 2011, Five Rivers Services was awarded a $7,022,503 firm fixed price with cost reimbursable line items contract modification to manage, operate, maintain, and logistically support the nine Air Force Space Surveillance System field stations, presumably for Fiscal Year 2012.[7]

A new space fence at Kwajalein Atoll in the Marshall Islands was declared operational on March 27, 2020.[17] In 2014 Lockheed Martin won the contract to build the new S band space fence system at Kwajelein with an option for another radar site in Western Australia.[2]

• GRAVES, in France
• Krona space object recognition station and Krona-N, in Russia